[IR] Remove an unnecessary cast (NFC) (llvm#147453)

predicate is already of Predicate.

Author: kazutakahirata

llvm/lib/IR/Instructions.cpp

@@ -3488,7 +3488,7 @@ CmpInst::CmpInst(Type *ty, OtherOps op, Predicate predicate, Value *LHS,
     : Instruction(ty, op, AllocMarker, InsertBefore) {
   Op<0>() = LHS;
   Op<1>() = RHS;
-  setPredicate((Predicate)predicate);
+  setPredicate(predicate);
   setName(Name);
   if (FlagsSource)
     copyIRFlags(FlagsSource);